This invention relates generally to ring laser angular rate sensors and more particularly to a mounting clip for retaining a getter inside a ring laser angular rate sensor.
A getter consists of a pure metallic material which, in the preferred embodiment of the present invention, is barium. A getter mounting clip is disposed within a block of a ring laser angular rate sensor in communication with the optical cavity of the sensor. The purpose of the getter is to have its material combine with unwanted non-noble gas components desorbed from the interior of the angular rate sensor optical cavity during storage and operation of the sensor. The getter is necessary since evacuation and subsequent noble gas fill does not accomplish a lasting cleanliness of the lasing gas. In order to maintain a long life of the ring laser angular rate sensor, it is important that only noble gases remain in the optical cavity during operation of the sensor.
U.S. Pat. No. 4,670,691 (U.S. Cl. 313/549) which issued to Podgorski on Jun. 2, 1987 describes a typical getter for a ring laser angular rate sensor.
A getter oxidizes during handling. The getter needs to be activated by heating at a high temperature, which may typically be 900.degree. C. for several minutes. This heating which occurs in a vacuum causes impurities on the surface of each grain in the getter to diffuse towards the getter interior. The getter surface is thereby cleaned and the getter is re-activated to absorb contaminating gas molecules, which it can do at room temperature. The getter is usually activated via a radio frequency (RF) arrangement. The RF activation affects the getter mounting clip as by heating the clip. This causes the mounting clip to lose its getter retaining characteristics which may cause the getter to be damaged by external vibrations or the like.
U.S. Pat. No. 4,503,543 which issued to Ljung, et al on Mar. 5, 1985 (U.S. Class 372/94) relates to a getter retainer or mounting clip having a resilient serpentine shaped tungsten wire formed to match a short wire section to hold a getter. The getter holder assembly so formed is positioned within a stepped oblong bore so that the getter is in firm contact with the bore surface at two points. This prevents resonances of the getter or getter mounting clip that might otherwise destroy the getter when subjected to vibrations. This particular device has the disadvantage of being difficult to manufacture and assemble.
U.S. Pat. No. 4,639,231 issued to Koper, et al on Jan. 27, 1987 (U.S. CLass 445/31) relates to a getter retainer or mounting clip wherein a groove is formed in a plate which is hermetically sealed to a hole in a ring laser angular rate sensor block. The cylindrically shaped getter is placed longitudinally in the groove such that the getter contacts the groove along only two lines. A mousetrap shaped spring preloads the getter against the groove so as to prevent acceleration forces and vibrations from causing pieces of the getter, heater coil or wire to break loose.
Neither of these devices appear to address the situation, as does the present invention, wherein the getter mounting clip is rendered less susceptible to RF activation of the getter.